Migrate to Rust 2024 Edition

[fischeti]

Bumps the Rust edition from 2018 to 2024, and modernizes the project structure in the following way:

• A new lib.rs file collects all the modules (previously done in main.rs), which is the new entry point of bender. This technically means that bender can now also be used as a library crate and not only a binary crate.
• main.rs is moved to bin/bender.rs and calls the bender library now (with the bender:: prefix)
• All extern crate are removed (not required anymore since the 2018 edition).
• cmd/mod.rs is replaced with cmd.rs, which collects all modules in cmd

Furthermore, new Rust editions typically change some formatting rules and some new clippy warnings surfaced (e.g. unused functions), which were fixed.

[micprog]

Some comments to help my understanding of the changes.

[micprog]

Is this part needed?

[fischeti]

You still need to return a a non-zero exit code somehow. You could also return a result instead, which will actually do the same thing:

fn main() -> Result<(), Box<dyn std::error::Error>> {
    bender::cli::main()?;
    Ok(())
}

However, the error will be debug formatted which is a bit uglz

[micprog]

Ok, I see the point! The current setup drops the preceding "error:" in red, if I'm not mistaken, so some adjustment is still needed... Is this where using anyhow or thiserror could be useful?

[micprog]

I'm not entirely sure this is the correct way to handle this... There may be a simpler way.

[micprog]

I'm not sure this is the correct way to handle this. If I'm not mistaken, this is a remnant from the original futures implementation, that was updated with async/await, but can probably be simplified now.

[micprog]

See above comments.